1. Field of the Invention
The invention is based on an actuator having a rotation angle sensor, and a method for manufacturing an actuator.
2. Description of the Prior Art
In a known actuator (DE 195 25 510 A1), a rotation angle sensor is provided for sensing an angular position of a rotor. Depending on the angular position of the rotor, a gas conduit extending through the housing of the actuator is opened to a greater or lesser degree by means of a throttle element connected to the rotor. In the known actuator, a first sensor part is situated on a gear connected to the rotor and a second sensor part is situated on a cover that is attached to the housing in a stationary fashion. In the actuator disclosed in DE 195 25 510 A1, the rotation angle is measured by means of moving sliders. It is, however, also possible to attach a magnet to the rotor, for example, and to attach a magnetically sensitive element to the stator. Depending on the position of the magnet of the rotor, the magnetic field acting on the magnetically sensitive element changes so that the magnetically sensitive element emits a corresponding electrical signal in accordance with the position of the rotor. Previously, the problem was the lack of a satisfactory solution for attaching the magnet to the rotor. For example, attaching the magnet to the rotor by means of screws would involve highly complex work. Casting the magnet into the plastic material of the rotor is also complex and requires a specific adaptation to different customer wishes and a significantly higher degree of complexity in the manufacture of the rotor. It is also possible to provide a deformable edge on the rotor, which is used by first placing the magnet against the rotor and then deforming the deformable edge so that the deformable edge encompasses part of the magnet, thus securing the magnet to the rotor. However, this has the disadvantage that the material normally used for the rotor, for example plastic, springs back slightly after the plastic deformation, thus resulting in play between the rotor and the magnet. As a result, the magnet can wobble somewhat in relation to the rotor. Another danger is that the deformation can change the properties of the plastic material of the rotor so that with the occurrence of temperature changes during operation of the actuator, the plastic material relaxes and as a result, the firm fit of the magnet is no longer assured. This leads to a distortion of the rotation angle sensor signal.